Model compounds for oxygen-transporting hemoproteins will be prepared and the effects of structure and environment on ligation with O2, CO and isonitriles studies. In particular cyclophane (pocket) hemes have been synthesized with variable pocket sizes. The steric hindrance to binding with these hemes will be studied by infrared spectra kinetic studies, and x-ray crystallography. Cooperative synthetic heme model systems, now in hand, will be studied as models of the cooperative ligation of hemoglobin.